The objective is to evaluate an alternate form of tonography for the differential diagnosis of glaucoma. This tonographic method known as Constant Pressure Tonography has been known to work in principle, but it has not been used in clinical practice because of a lack of an effective instrument to carry out this form of tonography. We believe that we have developed such an instrument and are now prepared to carry out the necessary biological test programs. The accuracy made possible by this instrument will make a significant improvement in the diagnostic value of Tonography. Standard tonography procedures now in use are believed to have errors tat range from 50 percent to 100 percent. Our analysis and laboratory tests indicate that we should beable to secure a precision of 10 percent to 20 percent in the measurement of aqueous facility. The nature of the work consists of 1) fabrication of special parts for the tonography instrument to further adapt it to the clinical environment; 2) laboratory testing and validation of instrument; 3) clinical evaauation using selected patients.